One type of material testing comprises bending an elongated, thin sample specimen under controlled conditions. Typically, the sample is mounted so that a probe contacting the center of the sample can apply a predetermined reciprocal bending force at a predetermined frequency. By measuring the frequency and amplitude response of the sample and comparing them with the driving force and frequency of the bending motor many properties of the sample material can be determined. These properties include the storage and loss moduli, the complex viscosity and tan delta. However, the manner of sample holding is critical. Previous sample holders often make precise centering of the probe tip difficult. Interchangeability and access to the probe tip also pose serious problems.